FIG. 1 is a schematic diagram of a workpiece processing system 100 in which a workstation 102 is coupled to an equipment front-end module (EFEM) 104. Workpieces handled manually or by robots (not shown) in EFEM 104 are delivered to or from the workstation 102 for processing in the workstation. Examples of workpieces include semiconductor wafers of various diameters, and substrates such as flat-panel displays. A pair of load locks 106 serve as interfaces between the vacuum environment of the workstation 102 and the EFEM 104, which is at atmospheric pressure.
Workstation 102 includes a vacuum transfer chamber (VTC) 108 surrounded by one or more processing stations 110 coupled at bays 111 of the VTC. The vacuum transfer chamber 108 houses a workpiece handling robot 112 in a vacuum environment. Workpieces, such as semiconductor wafer 114, are transferred by workpiece handling robot 112 from the load locks 106, to the various processing stations 110, and then back to the load locks. Workpiece handling robot 112 is equipped with an end effector 116 that engages the workpieces for pickup and transport between the load locks 106 and the processing stations 110. Each processing station 110 performs a particular processing task, such as chemical vapor deposition (CVD), plasma deposition, and the like, on the workpiece delivered to it by workpiece handling robot 112. Workpiece handling robot 112 may be equipped with multiple end effectors (only one is shown), and these may be independently actuatable in any of multiple degrees of freedom. The end effector(s) define the distalmost link in an articulated multi-link arm 118 of the workpiece handling robot 112. The number of links can vary depending on robot design.
It may be desirable under some circumstances to rotate, or flip, the workpiece so that it can undergo processing on an opposite side thereof. To conduct such flipping, workstation 112 must be suitably equipped. For example, robot arm 118, and specifically end effector 116, can be provided with an additional motor to impart roll motion to implement the flipping, and suitable clearance can be provided in the vacuum transfer chamber 108 for the flipping motion of the workpiece-end effector combination. However, in semiconductor processing environments, and particularly in the highly controlled vacuum transfer chamber region, “real estate” is at a premium, and expanding the size of the vacuum transfer chamber to provide flipping clearance for the workpiece-end effector combination is expensive and wasteful. This is exacerbated by the need to provide the additional motor, which occupies additional valuable space, and adds complication, weight, cost, and contaminants.
An alternative approach that is conventionally utilized is the dedication of one of the bays 111 to the flipping operation, by docking a specialized flipping station 120 to the VTC 108. The flipping motion can still be performed by the workpiece handling robot 112, which would then have to be suitably equipped (additional motor, etc.), to the detriments discussed above; or the flipping motion can be performed by a specialized mechanism (not shown) disposed in the dedicated flipping station 120. While the latter approach would eliminate the need for a flipping motion-capable robot, it ties up one of the bays 111, which would be better utilized for actual processing and increased throughput.